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Characterization of sialidase from bloodstream forms of Trypanosoma vivax
Author(s) -
Buratai L. B.,
Nok A. J.,
Ibrahim S.,
Umar I. A.,
Esievo K. A. N
Publication year - 2005
Publication title -
cell biochemistry and function
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 61
eISSN - 1099-0844
pISSN - 0263-6484
DOI - 10.1002/cbf.1189
Subject(s) - fetuin , sephadex , sialidase , enzyme , biochemistry , dithiothreitol , chemistry , sialic acid , hydrolysis , biology , microbiology and biotechnology , neuraminidase , glycoprotein
Sialidase (EC: 3.2.1.18) from Trypanosoma vivax (Agari Strain) was isolated from bloodstream forms of the parasite and purified to apparent electrophoretic homogeneity. The enzyme was purified 77‐fold with a yield of 32% and co‐eluted as a 66‐kDa protein from a Sephadex G 110 column. The T. vivax sialidase was optimally active at 37°C with an activation energy ( E a ) of 26.2 kJ mole −1 . The pH activity profile was broad with optimal activity at 6.5. The enzyme was activated by dithiothreitol and strongly inhibited by para‐hydroxy mercuricbenzoate thus implicating a sulfhydryl group as a possible active site residue of the enzyme. Theenzyme hydrolysed Neu5Ac2,3lac and fetuin. It was inactive towards Neu5Ac2,6lac, colomic acid and the gangliosides GM1, and GDI. Initial velocity studies, for the determination of kinetic constants with fetuin as substrate gave a V max of 142.86 μmol h −1 mg −1 and a K M of 0.45 m M . The K M and V max with Neu5Ac‐2,3lac were 0.17 m M and 840 μmole h −1 mg −1 respectively. The T. vivax sialidase was inhibited competitively by both 2,3 dideoxy neuraminic acid (Neu5Ac2,3en) and para‐hydroxy oxamic acid. When ghost RBCs were used as substrates, the enzyme desialylated the RBCs from camel, goat, and zebu bull. The RBCs from dog, mouse and ndama bull were resistant to hydrolysis. Copyright © 2005 John Wiley & Sons, Ltd.